It has been well known for a long time to subject metal work pieces to phosphatizing or other chemical treatment in a tank in which a two-phase fluid is present, the liquid phase being subjected to heat sufficient to form and maintain a vapor phase above it. See the patent to Sabatka, U.S. Pat. No. 3,896,829, granted July 29, 1975, and the publications set out therein where trichlorethylene is in solution with alcohols. When dirt from the metal work pieces contaminates the volatile two-phase treatment fluid to the point where the process is substantially impeded thereby, the treatment fluid must be removed from the treatment tank and replaced with clean treatment fluid.
Before the present invention, a leading purveyor of apparatus to perform the phosphatizing operation and of the chemicals used therein recommended the reclaiming of only up to half of the dirty treatment fluid by boiling and distillation. Continuation of the boiling and distillation process after half of the dirty treatment fluid has been boiled off and reclaimed was not recommended because of the fire hazard condition which resulted due to further concentration of the fluid. This is because the non-flammable constituents boil off first, leaving the flammable to boil off last.
If these recommendations are followed, the remaining concentrated dirty half of the treatment fluid has to be somehow disposed of hopefully without polluting the environment. The apparatus purveyor has no effective recommendations as to how this can be done.
Changing of fluid in a treatment tank utilizing 1800 gallons (6815 liters) of treatment fluid in liquid form results in the loss by disposal of 900 gallons (3408 liters) of treatment fluid. At a present cost of about $3.50 per gallon, this is a loss of $3150 per treatment fluid change.
An apparatus and method were needed to reclaim a much larger percentage of the relatively expensive and highly polluting treatment fluid in a manner which would not present a fire and explosion hazard; and to concentrate the contaminated, dirty and deleterious residue sufficiently so that it could economically and safely be completely disposed of.
To meet these needs, the apparatus and method of the present invention were developed.